Rough Rock (up to 30 m thick)
The Rough Rock forms an extensive outcrop to the immediate west of Sheffield and continues to West Yorkshire, where
it is worked for a wide variety of building stone products. It is mostly a coarse-grained feldspathic sandstone,
with cross bedding, but it is locally more thinly bedded, sufficient to be known separately as the Rough Rock Flags.
Indeed roofing flags from the Rough Rock or Rough Rock Flags were highly prized in the days before the coming of Welsh
slate (Figs. 21 and 22). The unit is still actively worked near Huddersfield for paving stones, as seen in the
Peace Gardens in the centre of Sheffield.
The base of the Rough Rock is often erosional and in places it rests upon another marine band, Gastrioceras cumbriense.
The Rough Rock forms a dominant feature in the landscape and often marks the edge of the predominantly moorland or rural
land use before the built-up areas of Sheffield and Barnsley on the Lower Coal Measures to the east (Fig.
23).